Generally collet-type chucks for use in bottle cappers have been known for many years and a wide range of specific designs for same have been suggested. Over the years, the unique requirements of such bottle cappers as compared to collet chucks used in such machine tools as lathes have become recognized and a distinct line of designs has been developed to meet these requirements.
Among these requirements have been the extremely high speed at which bottle capper chucks are caused to open and close and hence both the opening and closing thereof must be under a positive control. Further, the chuck jaws must be relatively loose in the surrounding casing, both to minimize frictional resistance to the desired high-speed operation and in recognition of the fact that the high-speed operation will result in rather substantial wear on the parts so that the precise dimensioning thereof cannot be permitted too high a level of criticality. These requirements have been well met by the chuck shown in the above-mentioned patent to Dimond, U.S. Pat. No. 3,537,321 and in the lineal predecessors of said patent, such as the patent to Dimond, U.S. Pat. No. 3,242,632. However, in this otherwise highly successful prior known device the necessary looseness of the jaws permits a certain amount of twisting or cocking of same when they are subjected to a driving force during otherwise normal operation. Where the cap to be screwed on is of relatively heavy material, this is no great disadvantage but when such cap is of a softer or more easily damaged material, such as a thin metal, then such cocking by the chuck jaws can produce a finished product which is unsightly at best and in many cases highly undesirable due to uneven tightening of the cap onto the bottle.
Particularly in the device of the above-mentioned patents, the jaws are driven from the surrounding casing or bell through a single pin which bears against one of said jaws. As said jaws are moved into and out from bottle cap gripping position a large number of times per minute, and the rotation of the chuck is started and stopped an equally large number of times per minute, the rotary and axial loads occurring between said pin and the driven one of said jaws are such as to cause a substantial twisting of said jaw with respect to said bell. The jaws are sufficiently aligned with each other that when the driven one thereof twists, the others will follow. This effects an irregular gripping of the bottle cap and also exerts a sufficiently concentrated pressure between a portion of each respective jaw, particularly the driven jaw and the surrounding casing or bell, as to rub off the lubrication applied thereto. This effects a very rapid wear of such jaw which in turn requires frequent readjustment of the chuck. Such readjustment requires downtime and inasmuch as this has in the past occurred every few hours, it means that the machine will have a certain amount of downtime at relatively short intervals.
Accordingly, the objects of the invention include:
1. To improve previously known chucks for bottle capping machines, particularly of the type illustrated in U.S. Pat. No. 3,537,231, to facilitate the smooth and accurate operation thereof.
2. To provide an improvement in chucks for a bottle capping machine, as aforesaid, in which the chuck elements are positively prevented from cocking or twisting in response to a rotating drive thereof.
3. To provide an improvement, as aforesaid, which will require a minimum of physical modification to the original equipment.
4. To provide a modification, as aforesaid, which can be carried out at a minimum of expense but which will ensure that the chuck jaws when gripped in driving condition will come much closer to defining a perfect circle than did the jaws of the above-mentioned previously known equipment.
5. To provide a device, as aforesaid, which will be operable in the same manner as the previously known equipment and which will be fully compatible therewith.
6. To provide a device, as aforesaid, which will be operable without downtime over much longer periods than has been obtainable from the apparatus known thus far.
Other objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspection of the accompanying drawings.